I put clothes in the dryer this morning, adjusted the setting, hit the start button and a flash came out from the back of the dryer. There's nothing back there except the plug and the hose to the exhaust that goes outside. I immediately stopped the dryer, checked everything out, started the dryer and it dried fine. Any ideas what caused that? Thanks for your help.

It could be the lint dust which accumulates in the vent. It may have ignited and then gone out. When was the last time you used a "coil brush" to clean out the vent? Also check the cord to the wall it may have a short. You may also want to look into the dryer drum at the back with a flash light. Lint also accumulates there, around the heater coils. If so vacuum it out through the holes on the back of the drum.